Begonia trees have pear flowers and pains. The disease is infected by two hosts. The first host is cypress, such as juniper, cypress and antlers. The second host is sessile begonia, begonia, hawthorn and so on. After the pathogen invades juniper and so on, pale yellow black spots will appear in the axils or branchlets of leaves in the first year, and then expand. By February and March of the following year, brown rice grains will occur and the epidermis will break, which is the winter spore angle. The winter spore horn is solitary or aggregated, which makes the plant branches expand. As the second host, Begonia sessilifolia infected with winter spore horn will appear yellow-green black spots on the front of leaves in early April-May, and then expand into circular yellow spots. A few small yellow spots will appear in the early stage of the lesion, and will turn dark black in the later stage, which will gradually thicken the corresponding parts of the back of the leaf, and some gray hairs will appear, which will turn into yellowish brown powder in August-September. In severe cases, the diseased leaves are full, the leaves are deformed and the appearance is uneven, which leads to premature death of the leaves and even plant death.

Prevention and control methods:

1. No cypress first host is planted around the sessile begonia.

2. During the onset, spray with 400 times of 20% Weixiuling EC. Or use 800 times of 50% triamcinolone acetonide wettable powder, spraying once every half month. Do not spray or spray less when the weather is dry.

3. In the middle and late March, when the full corn is about to swell in winter, use 0.3% sodium pentachlorophenol diluent and stone sulfur mixture to make Bomei 1 degree mixture, and spray it 2-3 times every half month to prevent it.